In: Biology
1
a. Addition of mineral oil is to create oxygen deficient condition (anaerobic environment) and since mineral oil sample are green color and with out oil tube exhibited yellow color, which is an indication of oxidase activity of bacteria in the tube (aerobic condition).
b. Aerobic bacteria will produce similar results; examples are E. coli, Lactobacillus etc.
2. Catalase is an enzyme which cleave hydrogen per oxide in to water and oxygen (bubble formation in catalase positive strain)
a. Aero tolerant anaerobes doesn't utilize catalase (catalase negative) instead of this they use another enzyme SOD (superoxide dismutase) and they can tolerate the presence of O2. Facultative anaerobe exhibits respiration in the presence (produces ATP) or absent of oxygen.
3. For the citrate test, bacteria are generally inoculated in a medium with following component
(i) Sodium Citrate
(ii) Bromothymol blue (it is known as pH indicator)
(In the presence of citrase)
Sodium citrate---------------------------à Oxaloacetate + acetate
a. Blue colour in the medium is an indicator of alkaline production also not color change is also an indicator of positive citrate formation
Citrate test positive bacteria is Klebsiella pneumoniae